1. Field of the Invention
The present invention relates to spacer fluid compositions, spacer fluid products, methods of well operation and well apparatus. In another aspect, the present invention relates to non-invasive (i.e., minimal loss to formation) spacer fluid compositions, non-invasive spacer fluid products, methods of well operation and well apparatus. In even another aspect, the present invention relates to cement spacer compositions, cement spacer products, methods of cementing wells, and hydrocarbon well apparatus. In still another aspect, the present invention relates to completion spacer compositions, completion spacer products, methods of well completion, and well apparatus.
2. Brief Description of the Related Art
In the drilling and completion of an oil or gas well, a cementing composition is often introduced in the well bore for cementing pipe string or casing in a process known as primary cementing. In primary cementing, a cementing composition is pumped into the annular space between the walls of the well bore and the casing. The cementing composition sets in the annular space, supporting and positioning the casing, and forming a substantially impermeable barrier/mass or cement sheath. An essential function of cementing is to prevent fluid exchange between the different formation layers through which the hole passes and to control the ingress of fluid into the well, in particular to limit the ingress of water. In production zones, the casing, the cement and the formation are all perforated over a depth of a few centimeters.
“Associative Polymers for Invasion Control in Water- and Oil-based Mudsand in Cementing Spacers Laboratory and Field Case Histories”, Reid et al., AADE-04-DF-HO-3, discloses that it has long been recognized that it is very desirable to minimize the invasion of drilling fluids, completion fluids, workover fluids and cements into subsurface formations. Further discloses that fluid invasion during drilling and completion operations causes many of the biggest problems faced in well construction. Even further discloses that in the payzone, invasion can produce formation damage as well as affect the quality of log information and fluid samples.
The prior art is replete with many disclosures of cementing in wells penetrating subterranean formations. In such operations, drilling fluids (often referred to as “muds”) are normally present in oil and other similar wells at the time of cementing a casing into a borehole with an aqueous cement slurry. Since the mud and cement are not always compatible with each other, it is often desirable to separate or prevent contact between them by use of a cement spacer system. Without the use of such spacer systems, the incompatibility of the aqueous cement slurry with the oil based mud is often of such severity that a mixture of the two forms an unpumpable mass. Such unpumpable masses may prevent displacement of at least a portion of the drilling fluid with a cement spacer system. Spacer systems also serve to water-wet the wellbore surfaces to promote bonding of the cement sheath to the wellbore and casing. Such cement spacer systems are often thought of as flushing agents.
In a typical operation, the cement spacer system is prepared at the site of entry into the well bore such that the density of the system matches or exceeds the densities of the fluids to be removed from the well and the like. In some commercial embodiments, mixing equipment for such applications may take the form of a 50 to 100 barrel “batch mixer” or be mixed “on the fly”. Some batch mixers may be hydraulically powered, self-contained unit that mix the cement spacer formulation immediately prior to the cementing operation. Such units are equipped with large paddles to facilitate the mixing of the cement spacer, centrifugal pumps for circulation of the spacer within the batch mixer and pressurized bulk storage tanks for the transport of the weighting agent for the cement spacer. Batch mixers may be truck-mounted or skid mounted depending on wellsite location requirements.
Once at the drilling site, the spacer system must be prepared from its constituent materials (typically water, gelling agent and weighting agent) and combined with any additional materials (such as surfactants or mutual solvents). The cement spacer system must then be tested for the appropriate density, with the density adjusted to fall within the appropriate range for the particular well bore. Independent of the particular chemistry of the cement spacer system, the storage time of the finished spacer prior to pumping into the wellbore is generally limited due to gravitational settling of the weighting agent.
U.S. Patent Application Publication No. 20100243236, published Sep. 30, 2010, by Koons, discloses nanoparticle-densified Newtonian fluids for use as cementation spacer fluids and completion spacer fluids in oil and gas wells. The publication discloses methods for densifying cement spacer fluids for use in conjunction with drilling fluids and cement slurries for cementing operations involving oil and gas wells, wherein such densifying is done via the addition of nanoparticles to the spacer fluid. Also disclosed are analogous methods of densifying completion spacer fluids using nanoparticles, to Newtonian fluid compositions resulting from any such fluid densification, and to systems for implementing the use of such compositions in well cementing operations.
U.S. Pat. No. 7,007,754, issued Mar. 7, 2006 to Fanguy, Jr., et al., discloses a method of cementing an area of a borehole with aqueous cement spacer system. The storable cement system comprises a suspending agent, a cement spacer and water. The composition may further optional contain a surfactant and/or an organic solvent and/or a weighting material. The suspending agent is preferably a carrageenan or scleroglucan. The cement system may be stored for an extended period of time prior to being interposed between a cement slurry and a drilling fluid. As such, the aqueous cement system may be made off-site and used when desired for preventing contact between non-compatible hydrocarbonaceous and aqueous fluids.
All of the patents cited in this specification, are herein incorporated by reference.
However, in spite of the above advancements, there exists a need in the art for compositions, products, methods and apparatus for well operations.
There also exists a need in the art for compositions, products, methods and apparatus for cementing wells.
There even also exists a need in the art for compositions, products, methods and apparatus for completing wells.
There still also exists a need in the art for non-invasive compositions, products, methods and apparatus for cementing wells.
There yet also exists a need in the art for compositions, products, methods and apparatus for cementing wells that prevent/reduce and/or minimize fluid loss.
There even still exists a need in the art for compositions, products, methods and apparatus for cementing wells that prevent/reduce and/or minimize gas displacement.
These and other needs in the art will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.